1. Technical Field
The present invention, in its several embodiments, relates to vehicle intercept methods and intercept processing structures and more particularly to the methods of, and processing systems for intercept estimation and interceptor guidance applied to maneuvering targets.
2. State of the Art
Because the process of proportional navigation of an interceptor does not yield a solution to the intercept of maneuvering targets, several advanced guidance laws and intercept geometry filtering techniques have been developed in attempts to accommodate the targets having time variation in the magnitude or direction of their respective velocity vectors. One approach in the construction of the filter and guidance law that has been applied to maneuvering target has been to use a target model, typically a discrete mathematical representation, in which the target is presumed to perform particular maneuvers. Based on such a target model, a guidance filter can be developed to estimate the relative target-to-interceptor position and velocity and target acceleration, as state estimates for example. Furthermore, the associated guidance law, which generates the interceptor's acceleration command using the state estimates, can be developed subject to the presumed engagement dynamics. However, a considerable drawback wit this target model approach is that the target acceleration cannot be easily modeled because the time history of the target acceleration is inherently a jump process whereby the acceleration levels and switching times are unknown a priori. Therefore, there remains a need for a more realistic target model and the associated filter and guidance law based on this target model.
Instead of presuming a target model, another approach for constructing the guidance law is to presume the worst possible target acceleration within the interceptor engagement scenario; i.e. the target is assumed to be intelligent, or at least aware of the interceptor, and tries to maximize the miss distance. In the problem formulation, the pursuer, i.e., interceptor, wishes to minimize the terminal miss whereas the evader, i.e., target, wishes to maximize it. Therefore, the guidance law for the interceptor is determined based on the anticipated worst possible target acceleration, i.e., based on game theoretic principals. Since this guidance law presumes that the engagement states are known by both players, the implementation requires that noisy information be processed through a filter. The filter that is usually chosen also presumes the worst possible target acceleration. However, if the target does not execute according to its assumed strategy, the filter performance can degrade rapidly, and thereby, produce large miss distances. Therefore, there remains a need for a accommodating filtering techniques that may be used with the type of guidance laws based on a game theoretic solution.